Re: Learning from other arts?
On the last paragraph I agree. Only by seeing the principles of what your doing and how they relate to natural phenomena in life, as you say to 'unite the fragments and techniques in oneself' can it finally become natural to you.
One motion naturally leading to another ie: irimi to tenkan, is based not on body mechanics but on natural non-resistive pathways of energy motion. So of course they can naturally flow into each other.
Personally I wouldn't let students practice things like kaeshi waza or nagashi waza until they thoroughly understood the above.